Look-A Like, Light Systems
Revised "OCT 20 2005"
Added info to correct Possible Problem on the Third Design.
If you have a problem with LED 1 staying Dimly Lit,
Takeanother Look at the Schematic and Overlay, NOW
In the First Circuit
By Changing the Values of the resistors on pins 6 and 7, And/Or the Capacitor
on pin 2 of the 555. you can changeFrequency.
I suggest you maintain an Aproximate 50% duty cycle.
This will give an Even Rise and Fall.
But reducing down to 25% can give a reasonable effect also!
In the Second CircuitIn the Second Circuit, the range of Frequency Adjustment should be Quite Sufficient as presented.
But the .47 cap can be changed in Value for other frequencies.
This Circuit is Better than myFirst Circuit above, as the waveform is more symetrical
and the Drive to the LM3914 is a more stable voltage with more current available.
Changes to the Ratio of the 470K to the 1M Resistor canaffect both the Frequency Range
as will as the Waveform Symetry. This could create a Sharp Rise and a Slow Decay,
or Visa Versa. Resulting in Different Visual Effects.
In the Third, NewestCircuit, The Simplest Circuit and Best Yet
The TL082 (Or a TL072 also is OK) Creates an Adjustable Sawtooth Generator.
(It also has a Square wave Output, but it isn't used here.)
The Left andRight LED's are Connected in Series and if this circuit is used on a
12 volt system, and if a person wanted to they could connect 2 LED's for each LED Shown.
Additionally I show the LED's Mountedon the Circuit Board, But they can be wired
OFF Board if So Desired.
1) There is a 1K Pot that adjust the Voltage input to the LM3914.
2) There is a 5K pot that adjust the Output voltage ofthe Sawtooth Oscillator.
3) There is a 250K Pot to set the Frequency as Desired.
4) Additionally there is a Connection point between Pin 9 of the LM3914.
Joining these together to creates a Bar...